1966 A904 loses all gears overnight

I drove my valiant ten miles and around for a couple days it shifted fine on point no slipping etc the next day it gets no gears it goes into park to keep the wheel locked but that it no reverse drive 1 2 3. Overnight weird so i changed the oil the filter was dirty, fresh oil new filter still nothings and before this i checked all the linkages ect it is engaging might it be the valve body inside? prior the trans was rebuilt about 6 years ago when it sat with no oil any ideas?